Re: should we enable log_checkpoints out of the box?

Hi,

On 2021-11-02 11:55:23 -0400, Robert Haas wrote:
> On Sun, Oct 31, 2021 at 10:59 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> > The general policy at the moment is that a normally-functioning server
> > should emit *no* log traffic by default (other than a few messages
> > at startup and shutdown). log_checkpoints is a particularly poor
> > candidate for an exception to that policy, because it would produce so
> > much traffic. No DBA would be likely to consider it as anything but
> > log spam.
>
> That's absolutely false. On any system where there's anything actually
> happening, there's going to be tons of stuff in the log because there
> are going to be failed connection attempts, queries that result in
> errors, and all kinds of other things like that. By any reasonable
> metric, the log volume of log_checkpoints=on is tiny.

Yes.

I think we do have significant issues with noisy mesages drowning out all
signal in the log, but that's largely stuff that's logged by default based on
client actions, at a high rate, rather than something occasional like log
checkpoints.

It's *hard* to find relevant stuff in postgres log files. Most instances with
some amount of traffic will have non-graceful disconnects (each logging two
messages, one "LOG: could not send data to client: Broken pipe" and one
"FATAL: connection to client lost"). It's normal to have some amount of
constraint violations. Etc. One cannot realistically see LOG or ERROR messages
indicating real trouble because we do not provide a realistic way to separate
such "normal" log messages from others fairly reliably indicating a problem.

> Besides appearing to be unwarranted mockery of what Bharath wrote,

Indeed.

Greetings,

Andres Freund